Preheat the oven to 350 degrees F.
Grease a 9-inch pie plate with the butter. Dust the dish with 1 tablespoon sugar, making sure you cover the sides too! I do this by holding the pie plate near-vertical and shimmying the sugar around the edge. Set the pie plate aside.
Using a stand mixer, an electric hand-mixer or a blender, mix the remaining 1/3 cup sugar, flour, 1/4 teaspoon salt, ginger, garam masala, eggs, milk, heavy cream and vanilla and let it go until the mixture is frothy.
Arrange the blackberries in the bottom of the pie plate (I don't like it to look too uniform), and carefully pour the batter into the dish.
Bake for 40 to 50 minutes, rotating the dish halfway to ensure even cooking. You'll know it's done when you insert a knife into the center and it comes out clean. Don't worry if certain areas puff up more than others as the clafouti cools on your counter it will even out.
Serve warm or at room temperature, dusted with a little powdered sugar, and topped with a little whipped cream, if desired. I like it just the way it is when it comes out of the oven!
Combine the cinnamon sticks, cloves, green cardamom seeds, black cardamom seeds, if using into a spice grinder or coffee grinder and grind until fine. Store the spice mix in an airtight container away from direct sunlight.